Types of Charges and Their Interactions

An electrostatic precipitator is a filterless device that removes polluted particles using the principle of charge attraction and repulsion. Negatively charged polluted gas enters an electrostatic precipitator as shown in this diagram. 

Which of the following situations is most likely to result in clean gas exiting the precipitator? 

Antistatic agents are added to some military jet fuels to make them safer to use. 

These agents impart electrical conductivity to the fuel. How does this prevent a spark-induced explosion?

This is a typical North American electrical outlet. 

The two large semi-lunar-shaped holes are called the safety grounds. These connections prevent any build-up of static charge that may occur when an electrical device is plugged into this outlet. What must these grounds be connected in order to work?